This invention relates to a pump actuator and more particularly to a pump actuator utilizing a novel variable pilot mechanism operably responsive to a control fluid flow which effectively regulates the delivery of an independent power fluid to a piston cylinder for cyclic operation of the piston therein.
Chemical injection pumps are used to introduce small, measured quantities of a chemical additive into a primary fluid flow line for admixture with the primary fluid, such chemicals including demulsifiers, methanol, corrosion inhibitors, etc. In general, these pumps are both controlled and operated by a single fluid flow to pressurize and depressurize a piston and cylinder assembly so as to move the operating piston through its power stroke upon cylinder pressurization and allow the piston return stroke upon cylinder depressurization. In one prior pump design, the cylinder pressure is fed back to a diaphragm-controlled valve arrangement to provide a fluid oscillator that controls the flow of fluid to and from the cylinder.
Although the oscillator-type pump is effective, the range and precision of adjustment of the cyclic rate of the piston are limited. Also, pumps of this type appear to be properly functioning even though the operating piston, due to malfunction, is not moving through its cycle.
Accordingly, recognizing this latter trait but more importantly to provide a pump which more effectively controls the cyclic rate and stroke of the operating piston, I have invented a chemical pump that does not utilize fluid pressure feedback to control the operating piston. My device utilizes a variable pilot mechanism having a pair of pressure responsive diaphragms forming a control fluid chamber therebetween. The diaphragms are movably responsive to chamber pressurization/depressurization as provided by a control fluid flow independent of a power fluid flow routed to and from the cylinder of the operating piston. This chamber pressure modification is provided by control fluid inlet and outlet valve assemblies which are actuated upon the completion of the power and return strokes of the operating piston. Upon diaphragm response, corresponding to the pressure modification of the pilot chamber, the cylinder inlet/outlet valves are alternately opened and closed to control the power fluid flow into and out of the cylinder. Accordingly, I have provided a pump actuator utilizing a variable pilot mechanism operably independent of the cylinder pressurization, which allows for an effective, finely tuned control of the cyclic rate of the operating piston. I have also provided means for adjusting the length of the power stroke therein independent of this cyclic rate control. Furthermore, if a malfunction occurs that causes the piston to stall, my pump will not falsely indicate that it is functioning normally.
It is therefore a general object of this invention to provide a pump actuator for controlling an injector device attached thereto, which utilizes a variable pilot mechanism, as operated by a control fluid, to regulate an independent power fluid flow to a power unit cylinder so as to effect the power and return strokes of the power unit piston.
It is another general object of this invention to provide a pump utilizing a variable pilot mechanism, as aforesaid, which is operably independent of the pressure of the power cylinder.
It is still a further object of this invention to provide a pump actuator utilizing a variable pilot mechanism, as aforesaid, which includes a diaphragmmatic pressure chamber therein for operating cylinder power fluid inlet and exhaust valve assemblies in response to control fluid pressurization and depressurization of said pressure chamber.
Another object of this invention is to provide such a variable pilot mechanism having associated control fluid inlet and outlet valve assemblies, operable in a timed relationship with the completion of the strokes of the operating piston so as to pressurize and depressurize the pressure chamber.
A particular object of this invention is to provide inlet and outlet valve assemblies for the control fluid which are cam actuated upon piston contact during the power and return strokes.
A further particular object of this invention is to provide a pump actuator of this type in which the length of the power and return strokes of the piston may be readily controlled.
Still another particular object of this invention is to provide a throttle assembly, independent of the stroke control, for regulating the rate of discharge of the power fluid from the cylinder to control the cyclic rate of the operating piston therein.
Another object of this invention is to provide a pump actuator, as aforesaid, which is lightweight, compact and easily transported by virtue of having pilot and power unit housings with control and power fluid conduits wholly located therein so as to present an internal network of functional power and control fluid paths.
Other objects and advantages of this invention will become apparent from the following description taken in connection with the accompanying drawings, wherein is set forth by way of illustration and example, an embodiment of this invention.